Thread rolling die with stabilizing portion

ABSTRACT

THIS INVENTON IS DIRECTED TO THREAD ROLLING DIES OF THE TYPE CAPABLE OF PRODUCING GIMLET POINTED SCREWS FROM HEADED CYLINDRICAL BLANKS. WHEN THE SCREW IS RELATIVELY SHORT, HAVING ONLY ONE TO A FEW TURNS OF THE THREAD ON THE BODY, IT IS OFTEN DIFFICULT TO START THE BLANK PROPERLY BETWEEN THE DIES. ACCORDINGLY, IN THIS INVENTION THE VERTICAL PORTIONS OF THE DIES AT THE LEADING ENDS ARE WIDENED TO PROVIDE ENOUGH THREAD GROOVES TO INSURE INITIAL STABILIZATION OF THE BLANK IN PROPER ROTATING ATTITUDE BEFORE THE BLANK REACHES THE CONVENTIONALLY SIZED POINTING AND SLUG PRODUCING PORTIONS OF THE DIES.

June 18, 1974 Q w, QRLQM0$K| ETAL Re. 28,049

THREAD ROLLING DIE WITH STABILIZING PORTION Original Filed April l. 1968HG. l A 4 /D YEG l E 24 i r--v-F-j \F /V M FIG. 2

United States Patent O Int. Cl. B21h 3/06 U.S. Cl. 72-469 5 ClaimsMatter enclosed ln heavy brackets [Il appears in the original patent butforms no part of this reissue specification; matter printed in italicsindicates the additions made by reissue.

ABSTRACT F THE DISCLOSURE This invention is directed to thread rollingdies of the type capable of producing gimlet pointed screws from headedcylindrical blanks. When the screw is relatively short, having only oneto a few turns of the thread on the body, it is often ditlicult to startthe blank properly between the dies. Accordingly, in this invention thevertical portions of the dies at the leading ends are widened to provideenough thread grooves to insure initial stabilization of the blank inproper rotating attitude before the blank reaches the conventionallysized pointing and slug producing portions of the dies.

SUMMARY OF THE INVENTION In the utilization of thread rolling dies ofthe type herein disclosed, one of the dies is held stationary in themachine and the other die is moved back and forth in parallelism andclosely adjacent thereto.

In producing screws, a headed blank with its axis in vertical positionis introduced between the leading ends of the dies. As relative diemotion commences, the blank is gripped and rotation begins along withinitial deformation. Usually the blank to be threaded is relatively longin relation to its diameter so, when gripped by the dies ofcorresponding vertical dimension, it starts its rotations in correctposition; that is, the axis is vertical and parallel to the die faces.

In the case of shorter screws in which the ratio of length to diameteris substantially decreased and particularly in the case of very shortscrews having one to a few turns of threads on the body, there is adistinct tendency for the blank, even though longer than the depth ofthe die, to become misaligned from correct axial position during initialrotation so that imperfect threads will be rolled.

This undesirable result is now overcome by changing the die constructionso that the leading portions of the vertical grooved die surfaces ofboth dies are of substantially greater vertical dimension thereby toinclude therein as many more thread grooves as have been foundcustomarily necessary to cause initial stabilized blank rotation.

After proper rotation is established and the threads formations havecommenced in the blank to the extent of perhaps one to two full turns,then the die surfaces of both dies may return to their normal verticaldimensions. Correct rotation and threading will then continue since thethread paths were well established at the outset. Likewise, the pointwill be formed and threaded by the conventional die construction and thesurplus material at the lower end of the blank will develop into aconventional slug to be cut off by the dies and discarded.

In making dies according to the present invention, no greater cost ofmaterials is involved since the widened part of the leading verticalsurface is a part of the die blank that heretofore would have beenground away in the forming of the reversely sloping slug producingsurface. In the present construction, the slug forming surface iscreated by removing only material from the die that is beyond theinitial widened portion. In this manner, the vertical width of that partof the die that conventionally would be available to grip initially theblank of a short screw may be more or less doubled without increasingthe cost of die material.

Tests may readily determine the minimum width of the leading ends of thedies to produce proper blank stabilization. Once this is achieved, thedie width may be reduced to the required dimensions for producing thescrew in question.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a bottom plan view of one ofa pair of dies.

FIG. 2 is a front elevation of FIG. l.

FIG. 3 is a section taken on the line 3-3 of FIG. 2.

FIG. 4 is a section taken on the line 4-4 of FIG. 2, including a screwthat has substantially completed at this position of the dies.

FIG. 5 is a section taken on the line 5-5 of FIG. 2.

FIG. 6 is a perspective view, somewhat forcshortened, of the die shownin bottom plan and elevation in FIGS. l and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings is shown asingle die generally referred to at 2. Those familiar with the art ofrolling threads by the use of at dies will recognize that die 2 isrepresentative of both required dies which are identical as far asoperative structure is concerned. The movable die is customarily madelonger at each end to facilitate entry of the blank between the dies andsafe discharge of the finished screw.

Accordingly, the description of die 2 will suffice for both dies whichare identical over equal comparable lengths. It might also be pointedout that the dies when in operative position in the screw producingmachine customarily have the grooved faces in vertical parallelposition. Thus, the main grooved surface A which produces the threads onthe body of the screw is, in use, in vertical position, although forconvenience, not so shown in FIGS. 3 to 6. Reference to the variousparts will hereinafter be made on the assumption that the surface A isvertical as it would be in normal use.

The top flat horizontal surface of the die is indicated at B.

The sloping surface which threads and points the screw is indicated at Cand intersects surface A along the heel line 3.

The vertical bumper surface, indicated at D, limits the setting of thetwo dies toward each other in the machine.

The reversely sloping surface E which intersects surface C along adiagonally extending edge 4 acts in cooperation with surface C to createsimultaneously the threaded screw point 6 (see FIG. 4) and the slug 7which is the unused and discarded lower end portion of the blank.

Referring particularly to FIGS. 2 and 6, the surface A of the finisheddie contains a plurality of side by side grooves 8 which in accord withwell understood principles, act to produce the threads I0 (see FIG. 4)on the body 12 of the blank as it is rolled between the dies. Thesegrooves 8 continue in correct direction in the sloping surface C toproduce the threads 14 on the screw point (see FIG. 4).

The underside of the screw head 16 (see FIG. 4) will rotate in slidingrelation along the top surface B of the die during the threading andpointing of the screw.

In the following explanation, it should be remembered that all die blanksurfaces (A, B, C, D, E, etc.) are completely formed before the threadgrooves are cut therein. Hence, reference to surfaces, ungrooved, in thecreation of the die will be understood as the initial forms thereof.

The manufacturing steps are as follows. First, the die blank is milledto produce the at surfaces A, C and D. Surfaces C and D initially extendthe full length of the blank. The dies are then cut away to produce thevertical wall F and the under wall G. The location and contour of wall Gwith respect to the top of the die B is controlled by the length of thescrew to be made. Each different length of screw, even of the same bodysize and number of threads per inch, calls for a separate pair of dies.The die inventory obviously for a complete line of screw sizes isextensive.

With the under wall G correctly formed, the next step is to generate thereversely turned surface E. This has been customarily done by a cuttingtool such as a milling cutter, for example, to cut away part of surfacesA and C starting at the dotted line 18 (see FIG. 6) and following thedotted lines 20 and 22 to continue in slightly upward and diagonaldirection to create the diagonal edge 4 and the lower edge 24 which isalso the boundary of under wall G.

The surface E narrowed by the convergence of edges 4 and 24 terminatesadjacent bumper surface D. The diagonal edge 4 preferably meets theupper edge 26 of bumper surface D so that formation and cut-off of theslug 7 will be assured when the screw has reached the position of line4--4 in FIG. 2 and as shown in FIG. 4.

Again, by reference to FIGS. 2 and 6, it is apparent that removal of thedie material bounded by dotted lines 18, 20 and 22 greatly reduces thevertical dimension of surface A (indicated by the bracket H) and thenumber of thread grooves thereafter to be cut into surface A incomparison with the vertical surface indicated by the bracket J thatwould otherwise be available.

When short screws are to be produced, it has been found that threads insurface A covering the distance H is generally insufficient to insurerolling stability in the blank. On the other hand, if all of surface Afor the vertical distance J were available for thread grooves, theninitial rolling stability of the blank would be assured.

Once the blank has commenced proper rotation, it will thereafter socontinue when reaching the narrower part of surface A where the diagonaledge 4 commences at the heel line 3 and close to section lines 3 3 ofFIG. 2 and as shown in FIG. 3.

According to the present invention, the full width J of surface A ispreserved to provide enough stabilizing thread grooves in the leadingpart of the die by creating the reversely sloping surface E in adifferent manner. The surface C which originally extended the length ofthe die is cut away in part over the length indicated by the bracket Min FIGS. l, 2 and 6 by a tool preferably moving crosswise rather thanlengthwise. In so doing, the lower part of surface A at the leading end(after the removal of the remaining part of surface C) remains untouchedto provide the full width I for receiving thread grooves. The surface Emay be created in various ways as by filing, grinding, shaping, milling,etc., the only requirement being that the intersection with surface C atthe edge 4 be sharp and straight and that the lower leading portion K ofthe surface A remain intact for receiving subsequent thread grooves.

In some special cases, it might be desirable to increase the dimension Jwhich can easily be done by shifting the boundary wall G at the leadingend to a lower level. The width of surface E in its initial stage belowthe dot dash line 28 is immaterial since that part of the surface doesnot engage the blank. Only that part of surface E above line 28functions to produce the slug. The width of surface E over the upperreaches thereof bounded by diagonal edge 4 and the lower edge 24 is notcritical. The angle of surfaces C and E with respect to surface A and toeach other to create a proper point on the screw and to produce andremove the slug effectively has been found to be approximately 20. Thisis shown in FIG. 5 taken on the line 5-5 of FIG. 2 where the length ofthe slopes on surfaces C and E are equal.

The 20 slope is a ligure commonly used in this type of die and is notconsidered part of this invention except insofar as the angles ofsurfaces C and E to each other must create a wedge configuration capableof producing the required point on the screw and the slug comprising thelower end of the blank that must be formed and discarded.

In the claims, the surface A is referred to as a vertical surface. Thisis only for convenience in defining the structure and is not to beconsidered limiting should the dies be utilized in other positions inspace which might be possible although in present practice is not done.

To make certain that blank rotation will occur, the surface A throughouta substantial part of its length may be cross-knicked in conventionalmanner as indicated by the lines X in FIG. 2. Similarly, the slugforming surface E may be cross-knicked as suggested by the lines X inFIG. 6.

Referring further to FIG. 2, it will be noted that if the heel line 3(which is the line of intersection of surface A and sloping surface C)is extended to the left it will intersect the left hand starting edge ofthe die at the point 30. The distance from the top B of the die toposition 30 is represented by the letter N, and the distance fromposition 30 to the bottom edge G of the starting end of the die isrepresented by the letter P. The overall vertical dimension of thestarting end of the die in which the grooves are present throughout theentire distance is represented by the letter l.

Referring again to FIG. 4, the dotted line 0 represents a vertical planewhich defines the location of the roots of all of the thread producinggrooves 8. The distance S is the horizontal distance from the plane 0 tothe line 26 which line as previously stated is the line of intersectionbetween the sloping grooved surface C and the bumper surface D. Alsoreferring to FIG. 4, the distance indicated by the letter L is thedistance from the top B of the die to the line of intersection 26 of thesloping grooved surface C and the bumper surface D.

In order to clearly distinguish the present invention over all prior artpatents which are at present known to the applicant and in which theremay be some accidental showing of grooves in the die at the starting endthereof that are located below the extension of the heel line at thestarting end of the die, applicant has in his main claims pointed outthat the thread grooves for the distance N above the heel line 3 in thewider area at the starting end of the die will be insucient bythemselves to insure stabilized rolling of the blanks but that thethread grooves over the total width J of the wider area which extendsabove and below the heel line 3 will be adequate lo insure blankstability.

No claim is made to the method of making the dies.

It is intended to cover all changes and modifications of the example ofthe invention herein chosen for purposes of the disclosure which do notconstitute departures from the spirit and scope of the invention.

I claim:

[1. A thread rolling die of the type described comprising a verticalgrooved surface for forming threads on the body of a blank, a slopinggrooved surface for pointing and forming threads on the point, avertical bumper surface extending downwardly from said sloping groovedsurface, a reversely sloping slug forming surface joining said slopinggrooved surface along a diagonal edge which commences at said verticalgrooved surface and terminates near said bumper surface, said verticalgrooved surface being substantially wider at that area thereof inadvance of said diagonal edge] [2. A thread rolling die of the typedescribed comprising a vertical surface having thread producing groovestherein, said surface being substantially wider at its leading end for alimited distance, a sloping surface having thread producing groovestherein intersecting the said vertical surface along the remainder ofits lower edge at the narrower part thereof, said intersection forming aheel line, a reversely sloping slug forming surface starting inside saidvertical surface and below said heel line at the beginning of saidnarrower part and extending upwardly and crossing the plane of saidvertical surface and intersecting said grooved sloping surface to form adiagonal edge on the leading portion of said sloping surface whichdiagonal edge commences at the said vertical Surface at the leading endof said heel line and terminates at the lower edge of said groovedsloping surface] [3. A thread rolling die of the type describedcornprising a vertical grooved surface for forming threads on the bodyof a blank, a sloping grooved surface for pointing and forming threadson the point intersecting said vertical grooved surface along a heelline, a vertical bumper surface extending downwardly from said slopinggrooved surface, a reversely sloping slug forming surface taperingtoward said bumper surface and intersecting said sloping grooved surfacealong a diagonal edge which commences at sai-d heel line and terminatesnear said bumper surface, said vertical grooved surface beingsubstantially wider and extending below said heel line at that areathereof in advance of said diagonal edge] [4. A thread rolling die ofthe type described comprising a vertical surface having a horizontalupper edge and having thread rolling grooves therein for producing athread on a blank, the vertical dimension of the said surr face engagingthe blank to be threaded decreasing substantially after a limitedinitial rolling distance has passed, a point forming ramp in the form ofa sloping grooved surface intersecting said vertical surface at thelatters narrower dimension along a heel line parallel to the upper edgeof said vertical surface, said ramp having a diagonal edge starting atsaid heel line and vertical surface and running toward the trailing endof the die and away from said vertical surface at a small angle thereto,and a slug forming and reversely sloping surface tapering in thedirection of said trailing end and terminating at said diagonal edge andhaving a length substantially coextensive therewith] [5. A threadrolling die of the type described comprising a vertical grooved surfacefor creating threads on the body of a cylindrical blank, said surfacebeing wide enough at the leading end to stabilize initial rotation ofsaid blank, said surface for the remainder of the die beingsubstantially narrower, and means commencing at the beginning of thenarrower portion for pointing and creating a thread on the said pointand means for simultaneously disposing of surplus blank material beyondsaid point, said last named means comprising a surface tapering in thedirection of movement of said blank] [6. A pair of dies for producinggimlet pointed screws from a blank by the rolled thread process, eachdie of said pair being of identical configuration over their cooperatingportions and comprising a vertical plane surface having a continuousstraight upper edge and having grooves therein for creating the threadson the body of the screw, a sloping plane surface having thereincontinuations of said grooves and extending away from said verticalsurface for creating the threaded pointed portion of said screw, theline of intersection of said vertical surface and said sloping surfaceforming a straight heel line, the said sloping surface having a diagonallower edge commencing at said vertical surface and extending generallylengthwise of said die and downwardly away from said heel line at asmall angle thereto, said sloping surface also having another lower edgecommencing at the end of said diagonal lower edge and being parallel tosaid heel line, said diagonal lower edge of said sloping surface formingthe upper edge of a reversely sloping slug forming and removal surface,said slug forming surface being a plane surface tapering in thedirection of movement of said blank and extending at least from thepoint of intersection of said diagonal edge and heel line to the pointof intersection of said diagonal edge and the lower parallel edge ofsaid sloping surface, said vertical plane surface at that part thereofin advance of the beginning of said diagonal edge being of greater widthand including more thread grooves than at that part between said heelline and the said upper edge of said vertical surface, whereby a blankentering said dies will initially be engaged by more thread grooves tostabilize its rotation before reaching the beginning of said diagonaledge and the fewer number of thread grooves in the remainder of saidvertical surface between said heel line and said upper edge] [7. Theconstruction set forth in claim 6 in which the angle of the said slopinggrooved surface to the said vertical grooved surface is approximatelythe same as the angle of the said reversely sloping slug forming surfaceto said vertical grooved surface] [8. The combination set forth in claim6 in which the lower portion of the die below said wider vertical areaand below said reversely sloping slug forming surface is cut away toprovide space for disposal of said slug when freed from said blank, andsaid die including a vertical bumper surface parallel to said verticalgrooved surface extending downwardly from the said lower edge of saidsloping grooved surface] 9. A thread rolling die of the type describedfor forming short gimlet pointed screws from blanks by the rolled threadprocess, said die comprising a vertical grooved surface A for formingscrew threads on the body of a blank, u sloping grooved surface Cintersecting said vertical grooved surface A along a heel line 3 forpointing and forming screw threads on the point, a bumper surface Dintersecting and extending downwardly from said sloping grooved surfaceC, a reversely sloping slug forming surface E joining said slopinggrooved surfoce C along a diagonal edge 4 which commences at saidvertical grooved surface A und terminates near said bumper surface D,said vertical grooved surface A being substantially wider at that areathereof in. advance of said diagonal edge 4 so that some of the groovesof the surface A at the said wider area are above the heel line 3 andsome of the grooves are below the heel line 3, the number of saidgrooves at the said wider area at the starting end of said die abovesaid heel line by themselves being insufficient to insure initialrolling stability of said blanks, but the number of said grooves abovesaid heel line plus the number of said grooves below said heel line atthe starting end of said die being sufficient to insure initial rollingstability of said blanks.

l0. A pair of dies for producing short gimlet pointed screws from blanksby the rolled thread process, each die of said pair being of identicaloperative conguration and comprising a vertical plane surface A havinggrooves 8 therein for creating the threads on the7 body of the screw, asloping plane surface C having therein continuations of said grooves 8and extending away from said vertical surface A for creating thethreaded pointed portion of said screw, the line of intersection of saidvertical surface A and said sloping surface C forming a straight heelline 3, the said sloping surface C having a diagonal lower edge 4commencing at said vertical surface A and extending generally lengthwiseof said die and downwardly away from said heel line 3 at a small anglethereto, said diagonal lower edge 4 of said sloping surface forming theupper edge of a reversely sloping slug forming and removal surface E,said vertical plane surface A at the starting end of said die and inadvance of the beginning of said diagonal edge 4 being of greatervertical dimension J and extending above and below the level of the heelline 3 so that some of the grooves of the surface A at the starting endof said die are above the heel line 3 at N and some of the grooves arebelow the heel line 3 at P. the number of said grooves at N at thestarting end of said die above said heel line by themselves beinginsufficient to insure initial rolling stability of said blanks but thenumber of said grooves at N above said heel line plus the number of saidgrooves below said heel at P at the starting end of said die beingsucient to insure initial rolling stability of said blanks.

11. A thread rolling die of the type described comprising a verticalgrooved suface for forming threads on the body of a blank, a slopinggrooved surface for pointing and forming threads on the pointintersecting said vertical grooved surface along a heel line, a verticalbumper surface extending downwardly from said sloping grooved surface, areversely sloping slug forming surface joining sloping grooved surfacealong a diagonal edge which commences at said vertical grooved surfaceand terminates near said bumper surface, said vertical grooved surfacebeing substantially wider at that area thereof in advance of saiddiagonal edge, the grooved surface above said heel line at the startingend of said die being incapable of initiating stabilized rolling withoutthe aid of the grooved surfaces below said heel line.

l2. A thread rolling die of the type described comprising a verticalgrooved surface for forming threads on the body of a blank, a slopinggrooved surface for pointing and forming threads on the pointintersecting said vertical grooved surface along a heel line, a verticalbumper surface extending downwardly from said sloping grooved surface, areversely sloping slug forming surface tapering toward said bumpersurface and intersecting said sloping grooved surface along a diagonaledge which commences at said heel line and terminates near said bumpersurface, said vertical grooved surface being substantially wider andextending in part below said heel line at that area thereof in advanceof said diagonal edge, the grooved surface above said heel line beingincapable by itself of initiating stabilized rolling of a blank.

I3. The construction set forth in claim 9 in which the dimension J atthe starting end of the die is substantially equal to the dimension L atdischarge end of the die.

References Cited The following references, cited by the Examiner, are ofrecord in the patented file of this patent or the original patent.

UNITED STATES PATENTS 3,176,491 4/1965 Mau et al. 72-469 X 3,196,6547/1965 Gordon 72-88 2,165,009 7/ 1939 Rosenberg 72-88 3,217,530 11/1965Sato 72-469 3,405,545 10/1968 Orlomoski 'l2-469 X 3,405,547 10/1968Orlomoski l2-469 MILTON S. MEHR, Primary Examiner

